• Smart Structures and Systems
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• 제20권6호
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• pp.709-728
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• 2017

This disquisition proposes a nonlocal strain gradient beam theory for thermo-mechanical dynamic characteristics of embedded smart shear deformable curved piezoelectric nanobeams made of porous electro-elastic functionally graded materials by using an analytical method. Electro-elastic properties of embedded curved porous FG nanobeam are assumed to be temperature-dependent and vary through the thickness direction of beam according to the power-law which is modified to approximate material properties for even distributions of porosities. It is perceived that during manufacturing of functionally graded materials (FGMs) porosities and micro-voids can be occurred inside the material. Since variation of pores along the thickness direction influences the mechanical and physical properties, so in this study thermo-mechanical vibration analysis of curve FG piezoelectric nanobeam by considering the effect of these imperfections is performed. Nonlocal strain gradient elasticity theory is utilized to consider the size effects in which the stress for not only the nonlocal stress field but also the strain gradients stress field. The governing equations and related boundary condition of embedded smart curved porous FG nanobeam subjected to thermal and electric field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is utilized to achieve the natural frequencies of porous FG curved piezoelectric nanobeam resting on Winkler and Pasternak foundation. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality parameter, electric voltage, coefficient of porosity, elastic foundation parameters, thermal effect, gradient index, strain gradient, elastic opening angle and slenderness ratio on the natural frequency of embedded curved FG porous piezoelectric nanobeam are successfully discussed. It is concluded that these parameters play important roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• Environmental Analysis Health and Toxicology
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• 제26권
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• pp.9.1-9.9
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• 2011

Objectives: In order to evaluate which temperature index is the best predictor for the health impact assessment of heat stress in Korea, several indexes were compared. Methods: We adopted temperature, perceived temperature (PT), and apparent temperature (AT), as a heat stress index, and changes in the risk of death for Seoul and Daegu were estimated with $^1{\circ}C$ increases in those temperature indexes using generalized additive model (GAM) adjusted for the non-temperature related factors: time trends, seasonality, and air pollution. The estimated excess mortality and Akaike's Information Criterion (AIC) due to the increased temperature indexes for the $75^{th}$ percentile in the summers from 2001 to 2008 were compared and analyzed to define the best predictor. Results: For Seoul, all-cause mortality presented the highest percent increase (2.99% [95% CI, 2.43 to 3.54%]) in maximum temperature while AIC showed the lowest value when the all-cause daily death counts were fitted with the maximum PT for the $75^{th}$ percentile of summer. For Daegu, all-cause mortality presented the greatest percent increase (3.52% [95% CI, 2.23 to 4.80%]) in minimum temperature and AIC showed the lowest value in maximum temperature. No lag effect was found in the association between temperature and mortality for Seoul, whereas for Daegu one-day lag effect was noted. Conclusions: There was no one temperature measure that was superior to the others in summer. To adopt an appropriate temperature index, regional meteorological characteristics and the disease status of population should be considered.

• 한국산학기술학회논문지
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• 제16권9호
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• pp.6180-6189
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• 2015

본 연구는 초등학생을 대상으로 스마트폰 중독에 미치는 영향요인을 규명하기 위한 서술적 조사 연구이다. 연구대상은 G광역시에 소재하는 4개 초등학교의 학생 263명이었다. 자료수집은 2014년 7월에 이루어졌으며, SPSS 19.0 program을 이용하여 분석하였다. 스마트폰 사용수준은 비중독군이 84.0%, 중독위험군은 16.0%로 나타났다. 일반적 특성 중 스마트폰 중독과 통계적으로 유의한 차이를 나타내는 특성은 학년, 동거가족, 경제적 수준, 성적, 사용동기, 사용시 좋은 점 및 사용시간이었다(p<.05). 스마트폰 중독은 충동성(r=.496, p<.001), 일상 스트레스(r=.471, p<.001)와 각각 양의 상관관계가 있었고, 부모의 양육태도(r=-.375, p<.001), 자아존중감(r=-.444, p<.001)과 각각 음의 상관관계가 있었다. 스마트폰 사용시간이 많을수록, 충동성이 높을수록, 일상 스트레스가 높을수록 대상자의 스마트폰 중독정도를 증가시켰다. 이러한 결과는 청소년 초기의 스마트폰 중독을 예방하는데 많은 관심을 기울여야 함을 시사하고 초기 청소년을 위한 스마트폰 중독 예방 프로그램을 개발하는데 기초자료로써 유용하게 활용될 것으로 사료된다.

• Journal of Preventive Medicine and Public Health
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• 제42권1호
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• pp.42-48
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• 2009

Objectives : This study was conducted to examine the factors implicated when people start smoking again after a 6 month cessation, and was carried out at the smoking cessation clinic of a public health center. Methods : The study subjects were 191 males who had attended the smoking cessation clinic of a public health center for 6 months in an attempt to quit smoking. Data was collected, by phone interview, regarding individual smoking habits, if any, over the 6 month study period. The factors which may have caused an individual to smoke again were examined. This study employed a health belief model as it theoretical basis. Results : Following a 6 month cessation, 24.1% of the study group began to smoke again during the 6 month test period. In a simple analysis, the factors related to individuals relapsing and smoking again included barriers of stress reduction, body weight gain and induction of smoking by surroundings among perceived barriers factor of our health belief model(p<0.05). In multiple logistic regression analysis for relapsed smoking, significant factors included barriers of stress reduction and induction of smoking by surroundings(p<0.05). The most important reason of for an individual to relapse into smoking was stress(60.9%) and the most likely place for a relapse to occur was a drinking establishment(39.1%). Conclusions : Our results indicate that both regular consultations and a follow-up management program are important considerations in a public health center program geared towards maintaining smoking cessation.

• 대한불안의학회지
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• 제14권2호
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• pp.135-141
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• 2018

Objective : This study evaluated the role of smartphone application in the self-assessment of three psychiatric symptoms: stress, depression, and suicidal ideation. Methods : A total of 5,646 respondents were evaluated with three scales (Perceived Stress Scale, PSS, Center for Epidemiologic Study for Depression, CES-D, Scale for Suicidal Ideation, SSI) via smartphone application 'mindscan'. We analyzed the sociodemographic variables, the levels of three symptoms, and the association between the scores on all three scales. Results : The mean total scores of PSS, CES-D, and SSI were 24.86, 35.15, and 18.03, respectively. Women showed significantly higher scores on PSS, CES-D, and SSI when compared with men. Younger users showed a significantly higher score on all three scales when compared with older users. The scores on all three scales were higher than in other studies with off-line surveys. The PSS was positively correlated with CES-D (r=0.690), and with SSI (r=0.367). The CES-D was positively correlated with SSI (r=0.540). Conclusions : A smartphone application for mental health based on three scales (PSS, CES-D, and SSI) is a relatively useful screening tool compared with off-line general population surveys. The association between the three scales reflects the relationship between the three psychiatric symptoms observed in clinical practice.

• 사회복지연구
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• 제39호
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• pp.29-56
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• 2008

본 연구는 남한에 장기 거주하는 북한 이탈 주민의 외상 경험 이후 심리적 성장 요인을 이해하기 위해서 실시되었다. 이를 위해서 남한 거주기간이 평균 7년 이상되는 탈북 주민 105명을 대상으로 외상 경험 이후 심리적 성장, 인구사회학적 요인, 개인 및 사회적 요인, 정신건강 요인, 북한 및 탈북과정의 외상과 남한 사회 스트레스를 측정하여 관련 변인들의 영향력을 분석하였다. 그 결과 북한에서의 학력과 제3국에서의 거주기간에 따라 PTG에 유의한 차이가 있었다. 탈북일, 우울, 문화적응스트레스, 미래에 대한 희망, 남한출신으로부터의 사회적지지, 인식된 만족은 PTG 와 유의한 상관이 있었다. PTG 예측요인으로 탈북일, 제3국체류기간, 문화적응스트레스 그리고 남한출신으로부터의 사회적지지로 나타났다. 이러한 연구결과를 바탕으로 정신건강 및 사회정책적 개입의 필요성을 논의하였다.

• 생물치료정신의학
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• 제24권3호
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• pp.230-238
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• 2018

Objectives : Among adolescents, the proportion of daily smoking tends to increase with age, and does not return to the previous level. Therefore, we examined the factors associated with smoking frequency in a nationwide sample of Korean adolescents to help prevent the progression of smoking. Methods : Among 127,804 adolescents who participated in the 2016 and 2017 Korean Youth Risk Behavior Web-Based Survey, data from 7,781 adolescents who replied that they currently smoked were analyzed. According to the frequency of cigarette smoking, participants were classified into daily and non-daily smokers. Participants' socio-demographic characteristics, smoking behavior, and psychological problems including perceived stress, depressive mood, and suicidality were assessed. Results : There were 3,627(47.4%) daily smokers and 4,154(52.6%) non-daily smokers. Low parental educational level, and early smoking experience were positively associated with daily smoking. High academic achievement, and high socio-economic status were negatively associated with daily smoking. Daily smoking was positively associated with lower happiness, lower sleep satisfaction, and severe stress during the past 12 months. Factors affecting suicide attempts of smokers were sex, residential type, socioeconomic status, and early smoking experience. Conclusion : The results indicated that socially disadvantaged families, and smoking experience with young age influenced daily smoking among Korean adolescents. Daily smoking was associated with psychological problems including lower happiness, lower sleep satisfaction, and severe stress. Early smoking experience influenced suicidal attempts among Korean adolescent smokers. Early intervention for smoking cessation in this high-risk group may contribute to prevention of these psychiatric complications of smoking.

• Advances in nano research
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• 제7권4호
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• pp.249-263
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• 2019

In the current paper, an exact solution method is carried out for analyzing the thermo-mechanical vibration of curved FG nano-beams subjected to uniform thermal environmental conditions, by considering porosity distribution via nonlocal strain gradient beam theory for the first time. Nonlocal strain gradient elasticity theory is adopted to consider the size effects in which the stress for not only the nonlocal stress field but also the strain gradients stress field is considered. It is perceived that during manufacturing of functionally graded materials (FGMs) porosities and micro-voids can be occurred inside the material. Material properties of curved porous FG nanobeam are assumed to be temperature-dependent and are supposed to vary through the thickness direction of beam which modeled via modified power-law rule. Since variation of pores along the thickness direction influences the mechanical and physical properties, porosity play a key role in the mechanical response of curved FG nano-structures. The governing equations and related boundary condition of curved porous FG nanobeam under temperature field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is utilized to achieve the natural frequencies of porous FG curved nanobeam supposed to thermal loading. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality parameter, porosity volume fractions, thermal effect, gradient index, opening angle and aspect ratio on the natural frequency of curved FG porous nanobeam are successfully discussed. It is concluded that these parameters play key roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• 동서간호학연구지
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• 제25권1호
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• pp.17-25
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• 2019

Purpose: This study investigated the factors influencing sleep quality in adults according to age groups. The escriptive study was conducted in metropolitan areas of South Korea to control for possible sleep differences between adults living in rural areas and those living in cities. Participants were 450 adults between 19 and 65 years old. Methods: Self-administered questionnaires consisting of including the Korean Modified Sleep Leeds Evaluation Questionnaire, the International Physical Activity Questionnaire and the Perceived Stress Scale were used to assess the quality of adults' sleep. Results: Sleep quality was poor across the all age groups Stress and subjective health status were influencing factors of sleep quality among participants in their 20s; subjective health status and circadian rhythm (evening-type) were influencing factors of those in their 30s; subjective health status, alcohol consumption, and work days of less than 8 hours were influencing factors among participants in their 40s; and stress, circadian rhythm (evening-type), subjective health status, work days of over 11 hours, past smoking habit, and light physical activity were influencing factors of those aged 50 years and over. Conclusion: The quality of sleep was low across the all adult age groups in South Korea. Although the factors influencing quality of sleep differed by age groups, they in general indicate the need to focus on maintaining and controlling health status in sleep interventions.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.1242-1242
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• 2022

Annually, several construction workers fall ill, are injured, or die due to heat-related exposure. The prevalence of work-related heat illness may rise and become an issue for workers operating in temperate climates, given the increase in frequency and intensity of heatwaves in the US. An increase in temperature negatively impacts physical exertion levels and mental state, thereby increasing the potential of accidents on the job site. To reduce the impact of heat stress on workers, it is critical to develop and implement measures for monitoring physical exertion levels and mental state in hot conditions. For this, limited studies have evaluated the utility of wearable biosensors in measuring physical exertion and mental workload in hot conditions. In addition, most studies focus solely on male participants, with little to no reference to female workers who may be exposed to greater heat stress risk. Therefore, this study aims to develop a process for objective and continuous assessment of worker physical exertion and mental workload using wearable biosensors. Physiological data were collected from eight (four male and four female) participants performing a simulated drilling task at 92oF and about 50% humidity level. After removing signal artifacts from the data using multiple filtering processes, the data was compared to a perceived muscle exertion scale and mental workload scale. Results indicate that biosensors' features can effectively detect the change in worker physical and mental state in hot conditions. Therefore, wearable biosensors provide a feasible and effective opportunity to continuously assess worker physical exertion and mental workload.